Radio frequency spectrum, which has been licensed to an operator grants exclusive use to the operator to deploy a mobile communications network (e.g. GSM, WCDMA/HSPA, LTE/LTE-A) using that licensed spectrum. As a result, the operator has exclusive control of the radio resources provided by the licensed spectrum. Since the first generation of cellular network deployments decades ago, licensed spectrum has traditionally been assigned to operators either via government-organised auctions, or so-called “beauty contests”.
Unlicensed spectrum is used by a number of technologies including Wi-Fi and Bluetooth. In contrast to licensed spectrum use, unlicensed spectrum can be shared and used among different technologies, which are not following any co-ordinated/centralised protection against interference. As a result performance of technologies in unlicensed spectrum is subject to unpredictable interference and therefore operation in unlicensed bands can be difficult.
A licensed cellular network technology like LTE would require new mechanisms that would allow it to co-exist with other radio access technologies and share unlicensed spectrum bands. Examples of such mechanisms are spread spectrum, frequency hopping, dynamic frequency selection, listen before talk and collision avoidance.
Deploying a mobile communications network in an unlicensed spectrum, which has been configured to operate in a licensed spectrum and therefore has previously been expected to have exclusive use of a contiguous set of communications resources represents a technical challenge.